This invention relates to rotary internal combustion engines. This invention also relates to rotary positive displacement apparatus such as fluid pumps and engines that utilise a toroidal cylinder for the working chambers.
Such internal combustion engines, fluid driven motors, fluid pumps and external combustion engines are hereinafter collectively referred to as toroidal engines. However, for illustrative purposes this invention will be exemplified hereinafter by reference to its internal combustion engine application.
Many forms of rotary engines have been contemplated and manufactured. Mostly they have been proposed as a means of reducing the inherent disadvantages associated with conventional reciprocating piston engines, and/or with a view to providing a compact or lightweight engine which is economical to manufacture and fuel efficient. To date these have not been commercialised. The only internal combustion engines which are mass produced are the Wankel rotary engine and the conventional reciprocating piston engine.
Conventional reciprocating pumps and engines have been universally utilised due to their efficient and simple conversion of reciprocating motion of the pistons, to a rotary motion via a crankshaft. However, conventional reciprocating internal combustion engines have fuel consumption limitations imposed by friction due to the multiplicity of moving parts. These moving parts generally include the bearing journals where friction increases with the speed of rotation and the number of bearings, the piston rings that impose friction by the plurality of rings on each piston, and the valve train where numerous components operate as a combined system that contributes significant friction to the engine as a whole.
In addition, thermal efficiencies of reciprocating internal combustion engines are reduced by the design of the mechanical components, the materials used, the manner of operation and, the use of a common cylinder portion for all the cycle phases. Fuel efficient conventional reciprocating internal combustion engines do exist but are highly complex units. Such complexity increases manufacturing and assembly costs.
The Wankel engine has found application in motor vehicles because of its high performance potential. However, for various reasons it has not been utilised for general use as a replacement for conventional piston engines such as commuter vehicles or mass produced small industrial engines.
Other forms of rotary engines have also been proposed. These include toroidal engines having a toroidal cylinder formed in the cylinder housing about a driveshaft assembly, rotor means supported for rotation about the driveshaft and coupled to pistons in the toroidal shaped cylinder whereby the pistons move cyclically toward and away from one another forming expanding and contracting working chambers therebetween within the toroidal cylinder, and, inlet and outlet ports extending through the cylinder housing assembly for entry and exit of fluid to and from the working chambers.
Typical prior art of toroidal engines are outlined in xe2x80x9cTHE WANKEL ENGINE DESIGN DEVELOPMENT APPLICATIONSxe2x80x9d by Jan P. Norbye published by the Chilton Book Company. French Patent No. 2498248 to Societe Nationale D""Etude et de Construction de Moteurs D""Aviation Snecma, and German patent No. 3521593 to Gebhard Hauser also illustrate prior art toroidal engines. Some of these engines utilise external mechanisms to effect the cyclic motion of the pistons, which move within the cylinder, while others utilise swash plates and cams and the like in the power train to achieve the desired mechanical coupling of the drive components.
For the purpose of mass production, it is considered that all this prior art has disadvantages either in inefficient configurations in terms of operation, or the ability to perform satisfactorily under normal working loads such as sustained optimum power delivery. Many of the prior proposals also require sophisticated manufacturing or assembly processes, are difficult to seal, are overly complex, or operate in an inefficient manner.
The present invention aims to provide toroidal engines which will alleviate at least one of the disadvantages outlined above.
With the foregoing in view, this invention in one aspect resides broadly in rotary positive displacement apparatus of the type having a toroidal cylinder formed in a cylinder housing assembly about a driveshaft with its axis concentric with the axis of the toroidal shaped cylinder and coupled to juxtaposed rotor assemblies having pistons in the toroidal shaped cylinder whereby rotation of the driveshaft rotates the rotors in a manner which causes the pistons to move cyclically toward and away from one another during their rotation, forming expanding and contracting working chambers therebetween within the toroidal cylinder and inlet and outlet port means extending through the cylinder housing assembly for entry and exit of fluid to and from the working chambers, and wherein the coupling means coupling the pistons in the toroidal shaped cylinder to the driveshaft includes:
drive means for coupling one rotor assembly to the driveshaft;
a crankpin offset from the driveshaft;
a planetary member driven for rotation about the crankpin at a predetermined rotational speed relative to the driveshaft whereby the planetary member is supported on the crankpin for epicyclic movement about the driveshaft, and
a direct drive connection between the other rotor assembly and the planetary member offset from their respective axes whereby the differential angular velocity of the direct drive connection about the driveshaft axis resultant from its epicyclic motion thereabout causes the pistons of the other rotor assembly to move cyclically toward and away from the pistons of the one rotor assembly as it rotates about the driveshaft.
The driveshaft may rotate in the same direction as the rotor assemblies but for most applications as an internal combustion engine it is preferred that the driveshaft is constrained to counter-rotate relative to the rotor assemblies whereby the speed of rotation of the rotor assemblies may be reduced relative to the speed of rotation of the driveshaft.
The drive means for rotating the planetary member about its orbiting axis may include a chain or toothed belt passing from a driven sprocket/pulley mounted on the planetary member concentric with the orbiting axis and about a drive sprocket/pulley mounted on the cylinder housing assembly. Alternatively the drive means may include a gear mounted on the planetary member and meshing internally or externally or indirectly through a gear train with a sun gear/annulus gear fixed to the cylinder housing assembly. Thus the planetary member may rotate with a planetary gear driven from a fixed sun gear co-axial with the driveshaft for rotating in the same direction as the rotor assemblies.
In the preferred form the planetary member rotates with a planetary gear driven from an annulus gear co-axial with the driveshaft whereby the driveshaft counter-rotates relative to the rotor assemblies.
The planetary member may be in the form of a lobed member constrained for epicyclic motion with respect to the driveshaft axis and cooperating directly with complementary lobes associated with the cylinder housing assembly. For example in an eight piston version the planetary member may be a six lobed member meshing externally with an eight lobed housing portion.
Preferably the driveshaft extends through the rotor assemblies and is mounted rotatably in bearings in the cylinder housing assembly at opposite sides of the rotor assemblies. The planetary member may be constrained for rotation about the driveshaft axis by being supported on a track formed in the support assembly and extending about the driveshaft, or on a crank type mounting rotatable about the driveshaft axis. Preferably however the driveshaft is in the form of a crankshaft forming the crankpin intermediate its mountings in the cylinder housing assembly and the planetary member is supported on the offset crankpin. Furthermore it is preferred that the crankshaft be formed with an intermediate floating journal on which the rotor assemblies are mounted.
It is also preferred that the direct drive connection is a drive pin which is located fixedly in one of either the planetary member or the other rotor assembly and which is slidable in the other to permit the epicyclic motion of the planetary member and whereby the load transfer between the fixedly located drive pin and either the planetary member or each rotor assembly is effected by transferring loads in a substantially straight load path through its slidable connection thereto. That is the load transfer is effected without the requirement of an interposed linkage or mechanism and it may thus be more robust, simpler, compact and reliable. Furthermore the direct drive connection enables all the mechanical workings to be constrained inwardly of the toroidal cylinder, the diameter of which is limited by sensible proportions and engine capacity, without sacrificing strength and durability.
Each drive pin may be bolted directly to a respective rotor assembly through a flange and suitably in the case where the drive pin extends to opposite sides of the rotors to engage with respective planetary members, the connection between the flange and the drive pin is offset so as to place a symmetrical load on the drive pin.
In a preferred form the planetary member is in the form of a drive yoke rotatable about the crankpin and having low friction slide means thereon extending away from the crankpin and engaged directly with the drive pin whereby the load transfer between the drive pin and the planetary member is transferred along a substantially straight load path through its slidable engagement with the planetary member.
The slide means could provide a non-linear slide path if desired but preferably the slide means extends radially away from the crankpin. The slide means suitably includes a radially extending slot in the drive yoke and a slide block freely slidable along the slot and carrying an axially extending drive pin which engages with the other rotor assembly. Preferably the slide block nests within a slot having a part circular profile whereby it is held captive in the slot, and in a preferred form the slide block is formed from a low friction material such as a ceramic material. If desired, the drive pin could engage directly in a rectangular sectioned slot or recess. Additionally, the drive pin could be integral with the slide block and/or the rotor assembly, but suitably the drive pin is a separate pin received rotatably in the slide block and the rotor assembly.
One of the rotor assemblies could be coupled to the driveshaft for rotation at a constant relative angular speed such that only the other rotor assembly oscillates relative to that one rotor to form the varying working chamber. It is preferred however that both rotor assemblies are coupled to the driveshaft in a corresponding manner.
In an internal combustion engine according to this invention, it is preferred that the pistons on the respective rotor assemblies alternately act as active and reactive pistons. In order to achieve the same dynamic loads for each rotor assembly when in their respective active or reactive phase, it is preferred that each drive yoke is formed with respective slide means extending radially away from diagonally opposite sides of the crankpin and that the respective drive pin thereof engages with a respective rotor assembly. This will cause the differential angular velocities of the opposed drive pins to move the active pistons cyclically away from the reactive pistons during an induction or expansion cycle and simultaneously cyclically toward the reactive pistons during a compression or exhaust cycle.
Furthermore, arranging the coupling means such that the coupled rotors are driven identically and out of phase has the advantage of maintaining an inertia balance of the components and equivalence of physical characteristics for all cycle phases. This is further assisted by the resultant near sinusoidal oscillating action of the rotors. In order to provide a more robust engine, the drive pins may extend through the rotor assemblies for direct coupling to corresponding drive yokes mounted at opposite sides of the rotor assemblies.
Suitably, the housing portions each form a complementary side portion of the toroidal housing and a respective portion of the annular access opening thereto. However this access opening could be formed in one housing portion if desired.
The number of pistons for each rotor of the rotary positive displacement apparatus may vary from a minimum of one per rotor. The engine may operate as a two stroke/cycle type engine or a four stroke/cycle type engine. Preferably, each pair of rotors has at least the number of pistons which corresponds to the number of cycles of the engine type with increases in piston numbers being in multiples thereof, for each pair of rotors. That is, for a two stroke/cycle type engine the total number of pistons may be 2,4,6,8 etc. whereas for a four stroke/cycle type engine the total number of pistons may be 4,8,12,16 etc. It is also preferred that the inlet and outlet port means comprises, for each minimum preferred number of pistons per engine type, an inlet port and an outlet port. Suitably the pistons on each rotor assembly are disposed equidistant about the outer portion of the respective rotors.
It is further preferred that the engine operate as a four stroke/cycle engine with the rotor assemblies being driven in the reverse direction to the crankshaft at an average rotational speed equal to one third thereof, that each rotor has a rotor body extending into and sealing the inside opening of the toroidal cylinder and four pistons disposed equidistant about the outer portion of the rotor body and that the inlet and outlet port means comprise a pair of diametrically opposed inlet ports and a pair of diametrically opposed outlet ports and that respective inlet and outlet ports are disposed in pairs of ports adjacent one another and adjacent the position of the pistons when disposed beside one another.
In a preferred embodiment the access means is an annular opening about the inside wall portion of the cylinder and the rotors are arranged in side by side relationship and extend into the opening to operatively seal this opening and support their respective pistons in the cylinder. The opening and the rotors may be asymmetrical about a centreplane containing the toroidal centreline of the cylinder but preferably the annular opening and the rotors are symmetrical about the centreplane. The cross-sectional configuration of the toroidal housing is suitably circular but it may be square or triangular or of other form as desired.
Preferably the rotor assemblies are substantially centrally disposed within the cylinder housing assembly and supported rotatably on a central journal of a crankshaft which has in-line crankpins at opposite sides of the central journal for supporting spaced pairs of aligned planetary members and the rotor assemblies support respective drive pins extending from opposite sides of the rotor assembly, through the adjacent rotor assembly, to each planetary member. In the embodiment having four pistons per rotor, identical but opposed rotors may be utilised with the drive pins offset 22.5 degrees from a line extending between opposed pistons. The radial location of the drive pins may also be varied to achieve variations in the relative movements of the pistons of the respective rotor assemblies.
The opening of the inlet and outlet ports could be timed by poppet valves or the like, but preferably, the inlet and outlet ports are formed in the cylinder wall and are timed by their arcuate length providing the selected communication with the working chambers. The ports could be formed in one housing portion, but preferably the inlet ports are formed in one housing portion and the outlet ports are formed in the other housing portion. Suitably the ports exit from opposed side walls of the toroidal cylinder but if desired they could exit at any angle or radially from either one or both cylinder housing assemblies, such as to enable banks of such assemblies to be stacked beside one another to form an engine having multiple toroidal cylinders arranged about a common crankshaft assembly.
It is also preferred that in an engine suitable for low speed high torque applications, such as for powering a commuting vehicle, the engine be formed such that the bore/stroke ratio is in the order of one is to three or one is to four, so that the combustion/expansion process achieves enhanced power extraction and minimises energy wastage. Suitably this is achieved in an engine having a cylinder bore diameter in the range of one quarter to one third the toroidal radius. Suitably the toroidal radius is between six to ten times the throw of the crankpin and the drive pin is offset from the crankshaft axis between three and five times the throw of the crankpin. In a preferred embodiment having four pistons per rotor the drive pins are spaced from the crankshaft axis four times the spacing of the crankpin therefrom and the toroidal axis is spaced from the crankshaft axis eight times the spacing of the crankpin therefrom.
Alternatively, an engine for high speed performance applications having twelve or sixteen pistons for each pair of rotors for example, may be formed with a bore/stroke ratio in the order of one is to one or one is to two.
In another aspect this invention resides broadly in an internal combustion toroidal engine of the type having a toroidal cylinder formed in a cylinder housing assembly about a driveshaft assembly supported for rotation about an axis concentric with the axis of the toroidal cylinder and coupled to axially opposed rotor assemblies supporting pistons in the toroidal cylinder by coupling means whereby rotation of the driveshaft causes the pistons to move cyclically toward and away from one another and vice versa, forming expanding and contracting working chambers therebetween within the toroidal cylinder and inlet and outlet port means extending through the cylinder housing assembly for entry and exit of fluid to and from the working chambers, and wherein:
the driveshaft is constrained for counter-rotation relative to the rotor assemblies whereby the speed of rotation of the rotor assemblies is reduced relative to the speed of rotation of the driveshaft.
In an internal combustion toroidal engine suitable for powering a medium sized car for comfortable highway cruising it is preferred that at 100 kph the average piston speeds be maintained in the order of 1100 fpm, which for an engine having a toroidal centreline radius of between 150 mm and 200 mm results in a rotational speed of the rotor assemblies of about 300 RPM.
This is preferably achieved by configuring the engine whereby the driveshaft rotates three times faster than the rotor assemblies, that is at about 900 RPM. This output shaft speed is accommodated using a final drive ratio of 1:1. For smaller vehicles similar proportions will exist. That is smaller wheel diameters will correlate to smaller toroidal cylinders with rotor assemblies rotating at higher speeds for the same piston speed.
In yet another aspect this invention resides broadly in a internal combustion toroidal engine of the type having a toroidal cylinder formed in a cylinder housing assembly about a driveshaft assembly supported for rotation about an axis concentric with the axis of the toroidal cylinder and coupled to axially opposed rotor assemblies supporting pistons in the toroidal cylinder by coupling means whereby rotation of the driveshaft causes the pistons to move cyclically toward and away from one another and vice versa, forming expanding and contracting working chambers therebetween within the toroidal cylinder and inlet and outlet port means extending through the cylinder housing assembly for entry and exit of fluid to and from the working chambers, and wherein the coupling means coupling the pistons in the toroidal shaped cylinder to the driveshaft includes:
drive means for coupling one rotor assembly to the driveshaft;
a crankpin offset from the driveshaft;
a planetary member driven for rotation about the crankpin at a predetermined rotational speed relative to the driveshaft whereby the planetary member is supported on the crankpin for epicyclic movement about the driveshaft, and the driveshaft is in the form of a crankshaft extending through the cylinder housing assembly and forming the crankpin intermediate its mountings in the cylinder housing assembly and the planetary member is supported on the offset crankpin.
In a further aspect this invention resides broadly in a rotary positive displacement apparatus of the type having a toroidal cylinder formed in a cylinder housing assembly about a driveshaft assembly supported for rotation about an axis concentric with the axis of the toroidal shaped cylinder and coupled to axially opposed rotor assemblies supporting pistons in the toroidal shaped cylinder by coupling means whereby rotation of the driveshaft causes the pistons to move cyclically toward and away from one another and vice versa, forming expanding and contracting working chambers therebetween within the toroidal cylinder and inlet and outlet port means extending through the cylinder housing assembly for entry and exit of fluid to and from the working chambers, and wherein:
the cylinder housing assembly includes respective opposed housing portions which mate along the centreplane of the toroidal cylinder;
the driveshaft assembly extends between the housing portions and is rotatably engageable with the respective opposed housing portions by loading opposite ends of the driveshaft axially into the respective opposed housing portions from the interior thereof, and wherein:
the coupling means comprises components which may be operatively assembled over the driveshaft from one or respective opposite ends thereof by interengagement of components in an axial direction whereby the rotary positive displacement apparatus may be readily assembled by sequentially adding components in an axial direction into operative engagement with one another.
Preferably the driveshaft is formed as a crankshaft and wherein the coupling means includes a drive yoke rotatable with a planetary gear about a crankpin assembly of the crankshaft with a planetary gear meshed with an internal annulus gear fixed to the adjacent housing portion concentrically with the driveshaft axis. The drive yoke may include a radially extending slot in which a slide block is fitted prior to assembly of the drive yoke onto the driveshaft. In such arrangement the slide block is suitably associated with a drive pin extending in the assembly direction into engagement with a rotor assembly.
Also, to facilitate assembly by loading components in an assembly direction, it is preferred that the drive yoke is driven by a planetary gear fixed to the drive yoke for rotation therewith and meshed with an annulus gear fixed to the housing with its axis coaxial with the driveshaft.
In still a further aspect this invention resides broadly in an internal combustion engine including:
a cylinder housing assembly having a toroidal shaped cylinder and an annular access opening to the cylinder;
a crankshaft assembly supported in the cylinder housing assembly for rotation about a crankshaft axis concentric with the axis of the toroidal shaped cylinder and supporting a crankpin assembly with its axis offset from the crankshaft axis;
a planetary member supported on the crankpin assembly for rotation about the crankpin assembly;
a pair of rotor assemblies, juxtaposed said planetary member and supported for rotation about an axis concentric with the axis of the toroidal shaped cylinder, each rotor assembly including a body portion supporting pistons, the total number of pistons for each pair of rotors being a multiple of four, the pistons being disposed equidistant about the body portions of the respective rotors and sealably engaged with the cylinder and moveable therearound, each body portion extending into the access opening to operatively close the toroidal cylinder;
coupling means coupling the planetary member and the rotor assemblies such that the coupled rotors and planetary member are carried around the crankshaft axis, and whereby rotation of the planetary member about the crankpin causes the rotor assemblies to move out of phase with respect to one another, and the pistons to move cyclically toward and away from one another forming expanding and contracting working chambers therebetween within the toroidal cylinder expanding and contracting between minimum and maximum working chamber volumes;
inlet and outlet port means extending through the cylinder housing assembly for entry and exit of fluid to and from the cylinder, the inlet and outlet port means comprising for each four pistons, an inlet port and an outlet port;
the inlet and outlet ports are disposed at positions at which adjacent pistons form minimum working chamber volumes;
drive means for rotating the planetary member about the crankshaft at a relative rotational speed whereby the inlet port means successively opens in a constant timed relationship to an expanding working chamber and the outlet port means successively opens in a constant timed relationship to a contracting working chamber.
Preferably, the internal combustion engine includes a duplicate planetary member mounted on a further in-line crankpin at the opposite side of the rotor assemblies, and coupling means coupling the duplicate planetary member to the rotor assemblies. It is also preferred that the internal combustion engine has the cylinder housing assembly formed as a split housing, split along the centreplane containing the toroidal centreline of the cylinder to form opposed housing parts, which are spaced apart along an inside portion of the cylinder housing assembly to form the annular access opening, the planetary members supported in spaced apart relationship on respective co-axial crankpins for rotation thereabout, and coupling means which includes respective slide means associated with the planetary members having diametrically opposed slides engaging respective drive pin assemblies which extend parallel to the crankshaft axis and from opposite sides of each rotor assembly to each planetary member.
The crankshaft may be a built-up shaft or it may be a one-piece shaft. The crankshaft may include a central rotor bearing integral with or detachably mounted to the crank-pins and if desired detachable main bearings which secure to the outer ends of the crankpins to facilitate ease of assembly of the engine components and/or use of one-piece rotors and planetary members. Alternatively a one-piece crankshaft may be used together with split planetary members which can be secured about the respective crankpins without being passed across the outer main bearings.